Alzheimer's disease is the most prevalent form of senile dementia. Epidemiological studies suggest that 25-50% of all people in their 80's have Alzheimer's disease. Generally, the first symptom of Alzheimer's disease is memory loss, followed by a decline in reasoning ability and reduced use of speech. Behavioral disorders are also often present. The deterioration appears to be irreversible, and eventually leads to death. There is no effective treatment currently available.
Alzheimer's disease was originally described, and is still diagnosed, based on the presence in the postmortem brain of pertinacious deposits, known as amyloid plaques, which stain with the dye Congo Red. Amyloid plaques contain a core comprising ordered fibrillar protein aggregates. In Alzheimer's disease, the predominant brain amyloid proteins are .beta.1-42 and its C-terminally truncated relative .beta.1-40.
Determination of amyloid load is typically accomplished by counting Congo Red stained amyloid plaques per microscopic field in brain tissue sections of subjects during autopsies. There is a need for probes which allow localization and quantification of amyloid deposits and which can be used in live persons so as to non-invasively diagnose the presence of Alzheimer's disease and/or monitor the efficacy of different treatments for Alzheimer's disease.
There is also a need for such probes for certain other neurodegenerative diseases which affect various mammals, e.g., the prion diseases, e.g., scrapie, bovine spongiform encephalopathy ("mad cow disease"), and Creutzfeldt-Jacob disease.